Vscode + Haskero: "Couldn't guess that module name" instead of type hovers

I like the "type hover" feature in Haskero. But if my code contains mistakes, the hover says "Couldn't guess that module name" instead of showing types. Is it a proper behavior? Because this "type hover" feature seems to be useful when fixing mistakes.

I realized there is a weird fix:

1. Fix the code no matter how, so it will compile.
2. Ctrl S. (Type hovers start to work)
3. Return the original code with a mistake.
4. Ctrl S.

After this, I still see type hovers (and no error).